(C++) boost::numeric::ublas::matrix example 4: chop

 

boost::numeric::ublas::matrix example 4: chop is a Boost.uBLAS library example.

 

• Download the Qt Creator project 'CppUblasMatrixExample4' (zip)

 

 

 

 

 

 

Technical facts

 

Application type(s)

• Desktop application

Operating system(s) or programming environment(s)

• Lubuntu 12.10 (quantal)

IDE(s):

• Qt Creator 2.5.2

Project type:

• Console application

C++ standard:

• C++11

Compiler(s):

• G++ 4.7.2

Libraries used:

• STL: GNU ISO C++ Library, version 4.7.2

 

 

 

 

 

Qt project file: CppUblasMatrixExample4.pro

 

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TEMPLATE = app CONFIG += console CONFIG -= qt QMAKE_CXXFLAGS += -std=c++11 SOURCES += main.cpp

 

 

 

 

 

main.cpp

 

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#ifdef _WIN32 #undef __STRICT_ANSI__ #endif #include <boost/numeric/ublas/io.hpp> #include <boost/numeric/ublas/matrix.hpp> #include <boost/numeric/ublas/matrix_proxy.hpp> const boost::numeric::ublas::matrix<double> CreateMatrix(   const std::size_t n_rows,   const std::size_t n_cols,   const std::vector<double>& v) {   assert(n_rows * n_cols == v.size());   boost::numeric::ublas::matrix<double> m(n_rows,n_cols);   for (std::size_t row = 0; row!=n_rows; ++row)   {     for (std::size_t col = 0; col!=n_cols; ++col)     {       m(row,col) = v[ (col * n_rows) + row];     }   }   return m; } //Chop returns a std::vector of sub-matrices //[ A at [0]   B at [1] ] //[ C at [2]   D at [4] ] const std::vector<boost::numeric::ublas::matrix<double> > Chop(   const boost::numeric::ublas::matrix<double>& m) {   using boost::numeric::ublas::range;   using boost::numeric::ublas::matrix;   using boost::numeric::ublas::matrix_range;   std::vector<matrix<double> > v;   v.reserve(4);   const int midy = m.size1() / 2;   const int midx = m.size2() / 2;   const matrix_range<const matrix<double> > top_left(    m,range(0   ,midy     ),range(0   ,midx     ));   const matrix_range<const matrix<double> > bottom_left( m,range(midy,m.size1()),range(0   ,midx     ));   const matrix_range<const matrix<double> > top_right(   m,range(0   ,midy     ),range(midx,m.size2()));   const matrix_range<const matrix<double> > bottom_right(m,range(midy,m.size1()),range(midx,m.size2()));   v.push_back(matrix<double>(top_left));   v.push_back(matrix<double>(top_right));   v.push_back(matrix<double>(bottom_left));   v.push_back(matrix<double>(bottom_right));   return v; } bool IsAboutEqual(const double x, const double y) { return std::abs(x-y) < 0.00001; } int main() {   using boost::numeric::ublas::matrix;   using boost::numeric::ublas::prod;   using boost::numeric::ublas::vector;   {     //                     [ 1.0 ] | [ 2.0   3.0 ]     // [ 1.0 2.0 3.0 ]     --------+--------------     // [ 4.0 5.0 6.0 ]     [ 4.0 ] | [ 5.0   6.0 ]     // [ 7.0 8.0 9.0 ] ->  [ 7.0 ] | [ 8.0   9.0 ]     const matrix<double> m = CreateMatrix(3,3, {1.0,4.0,7.0,2.0,5.0,8.0,3.0,6.0,9.0} );     assert(m(0,0) == 1.0); assert(m(0,1) == 2.0); assert(m(0,2) == 3.0);     assert(m(1,0) == 4.0); assert(m(1,1) == 5.0); assert(m(1,2) == 6.0);     assert(m(2,0) == 7.0); assert(m(2,1) == 8.0); assert(m(2,2) == 9.0);     const std::vector<matrix<double> > n = Chop(m);     assert(n.size() == 4);     std::clog       << "m   : " << m    << '\n'       << "n[0]: " << n[0] << '\n'       << "n[1]: " << n[1] << '\n'       << "n[2]: " << n[2] << '\n'       << "n[3]: " << n[3] << '\n';     assert(n[0].size1() == 1);     assert(n[0].size2() == 1);     assert(n[1].size1() == 1);     assert(n[1].size2() == 2);     assert(n[2].size1() == 2);     assert(n[2].size2() == 1);     assert(n[3].size1() == 2);     assert(n[3].size2() == 2);     assert(n[0].size1() + n[2].size1() == m.size1());     assert(n[1].size1() + n[3].size1() == m.size1());     assert(n[0].size2() + n[1].size2() == m.size2());     assert(n[2].size2() + n[3].size2() == m.size2());   }   {     const matrix<double> m = CreateMatrix(5,5,       {         1.0, 6.0,11.0,16.0,21.0,         2.0, 7.0,12.0,17.0,22.0,         3.0, 8.0,13.0,18.0,23.0,         4.0, 9.0,14.0,19.0,24.0,         5.0,10.0,15.0,20.0,25.0       }     );     assert(m(0,0) ==  1.0); assert(m(0,1) ==  2.0); assert(m(0,2) ==  3.0); assert(m(0,3) ==  4.0); assert(m(0,4) ==  5.0);     assert(m(1,0) ==  6.0); assert(m(1,1) ==  7.0); assert(m(1,2) ==  8.0); assert(m(1,3) ==  9.0); assert(m(1,4) == 10.0);     assert(m(2,0) == 11.0); assert(m(2,1) == 12.0); assert(m(2,2) == 13.0); assert(m(2,3) == 14.0); assert(m(2,4) == 15.0);     assert(m(3,0) == 16.0); assert(m(3,1) == 17.0); assert(m(3,2) == 18.0); assert(m(3,3) == 19.0); assert(m(3,4) == 20.0);     assert(m(4,0) == 21.0); assert(m(4,1) == 22.0); assert(m(4,2) == 23.0); assert(m(4,3) == 24.0); assert(m(4,4) == 25.0);     const std::vector<matrix<double> > n = Chop(m);     assert(n.size() == 4);     std::clog       << "m   : " << m    << '\n'       << "n[0]: " << n[0] << '\n'       << "n[1]: " << n[1] << '\n'       << "n[2]: " << n[2] << '\n'       << "n[3]: " << n[3] << '\n';     assert(n[0].size1() == 2);     assert(n[0].size2() == 2);     assert(n[1].size1() == 2);     assert(n[1].size2() == 3);     assert(n[2].size1() == 3);     assert(n[2].size2() == 2);     assert(n[3].size1() == 3);     assert(n[3].size2() == 3);     assert(n[0].size1() + n[2].size1() == m.size1());     assert(n[1].size1() + n[3].size1() == m.size1());     assert(n[0].size2() + n[1].size2() == m.size2());     assert(n[2].size2() + n[3].size2() == m.size2());   } } /* Screen output: m   : [3,3]((1,2,3),(4,5,6),(7,8,9)) n[0]: [1,1]((1)) n[1]: [1,2]((2,3)) n[2]: [2,1]((4),(7)) n[3]: [2,2]((5,6),(8,9)) m   : [5,5]((1,2,3,4,5),(6,7,8,9,10),(11,12,13,14,15),(16,17,18,19,20),(21,22,23,24,25)) n[0]: [2,2]((1,2),(6,7)) n[1]: [2,3]((3,4,5),(8,9,10)) n[2]: [3,2]((11,12),(16,17),(21,22)) n[3]: [3,3]((13,14,15),(18,19,20),(23,24,25)) */